Question

which field did you set as the primary key in tblmembers table?
bookid
returnid
membername
memberid

Explanation:

A primary - key uniquely identifies each record in a table. In a tblMembers table, MemberID is most likely to be the primary key as it is a unique identifier for each member. BookID is related to books, ReturnID to returns, and MemberName may not be unique (multiple members could have the same name).

Answer:

D. MemberID